Laser speckle contrast imaging: theoretical and practical limitations

TLDR: LSCI is used primarily to map flow systems, especially blood flow, and its limitations and problems are investigated.

Abstract: When laser light illuminates a diffuse object, it produces a random interference effect known as a speckle pattern. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can provide infor- mation about the movement. A simple way of accessing this information is to image the speckle pattern with an exposure time longer than the shortest speckle fluctuation time scale—the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus, velocity distributions are coded as speckle con- trast variations. The same information can be obtained by using the Doppler effect, but producing a two-dimen- sional Doppler map requires either scanning of the laser beam or imaging with a high-speed camera: laser speckle contrast imaging (LSCI) avoids the need to scan and can be performed with a normal CCD- or CMOS-camera. LSCI is used primarily to map flow systems, especially blood flow. The development of LSCI is reviewed and its lim- itations and problems are investigated. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.